1. Technical Field
The present invention generally relates to integrated circuit packaging and in particular to an improved ceramic package. Still more particularly, the present invention relates methods for designing and fabricating ceramic packages with hybrid mesh layers for improved performance.
2. Description of the Related Art
Ceramic packages, such as glass ceramic (GC) or 9211 modules, are becoming a popular option for fabrication of integrated circuit (IC) modules. With these ceramic packages/modules, the metal layers comprise of mesh planes instead of solid metal planes. Typically, the signal layer(s) in which high speed signals propagate have mesh planes located above and below the signal layer in order to provide path(s) for high frequency return current. The mesh plane design includes discontinuities within the mesh planes. These discontinuities make the high frequency signal return path worse, leading to higher near end (NE) and far end (FE) crosstalk coefficients (which are defined by crosstalk amplitude per unit length of a signal line).
One of manufacturing limitations of these kinds of ceramic module (i.e., those designed with mesh planes) is that the metal loading (i.e., the amount of metal area versus total area of a layer) is limited. For example, with GC modules, the ratio of metal area to total area is capped at about 30%, while with 9211 modules, that ratio is caped at about 40%. There are specific limitations, including yield issues, which are manifest when/if the metal loading in the ceramic module is higher than these respective ratios. Additionally, the metal loading ratios also indicates how much copper (Cu) paste is required for manufacturing the ceramic modules, and the amount of Cu directly affects the manufacturing cost for the ceramic modules.